Shock wave lithotripsy (SWL) is the first line treatment for the majority of patients with kidney stones. The gold standard in SWL is still considered to be the Dornier HM3, which was the first lithotripter introduced into the US. The HM3 is an electrohydraulic lithotripter (EHL) that uses a single underwater sparker as a shock wave source. The HM3 has the drawback that the electrodes erode quickly and must be replaced in the middle of a procedure, and causes significant side effects. This project is to develop optimized arrays several sparkers in small ellipsoidal reflectors that last for several procedures and break stones more effectively. The flexibility in placement of the sparkers allows space for an in-line probe to monitor stone location during treatment, which will result in fewer pressure pulses missing the stone and reduce damage to surrounding tissue. The specific project objectives are to optimize sparker arrays, including the use of double pulses by breaking both artificial and actual kidney stones, develop an in-line probe and conduct animal studies to investigate side-effects and to support an IDE. A successful Phase II will lead to the development of a prototype and clinical studies and subsequent commercialization.